TROUBLE SHOOTING¶

Could not connect to display¶

While trying to run EXtra-foam remotely on the online cluster (exflonc12, etc), if you end up with error messages similar to,

qt.qpa.xcb: could not connect to display
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized.
Reinstalling the application may fix this problem.

please make sure that you have done X11 forwarding while logging to the online cluster. Using EXtra-foam on Maxwell cluster, it is better to use FastX2 at max-display as explained in previous section.

Shut down the redis server?

If you are prompted to warnings like,

[user@exflonc12 ~]$ extra-foam DSSC SCS

services.py - WARNING - Found Redis server for DSSC (started at 2020-02-06 12:50:03.906872)
already running on this machine using port 6380!

You can choose to shut down the Redis server. Please note that the owner of the Redis server
will be informed (your username and IP address).

Shut down the existing Redis server? (y/n)

EXtra-foam uses Redis as broker to pass meta information between different processes. By design, each type of detector has its unique Redis port so one can safely run more than one EXtra-foam instances for different detectors on the same machine. However, it is not allowed to run two instances with the same type of detector. Also, EXtra-foam receives data from karabo bridge and thus there can be data loss if there is any instance secretly running in the background, stealing the data.

In the instrument control room, there should be only one EXtra-foam instance for the detector that is running. Therefore, it is safe to type “y” to shut down the existing Redis server. However, if somebody wants to make a joke about you and did that remotely, you will get informed.

Config file is invalid¶

If you are prompted to warning like,

Traceback (most recent call last):
  File "/home/username/anaconda3/envs/foam/bin/extra-foam", line 11, in <module>
    load_entry_point('EXtra-foam', 'console_scripts', 'extra-foam')()
  File "/home/username/xfel-data-analyais/EXtra-foam/extra_foam/services.py", line 356, in application
    config.load(detector, topic)
  File "/home/username/xfel-data-analyais/EXtra-foam/extra_foam/config.py", line 456, in load
    self._data.load(detector, topic)
  File "/home/username/xfel-data-analyais/EXtra-foam/extra_foam/config.py", line 382, in load
    self.from_file(det, topic)
  File "/home/username/xfel-data-analyais/EXtra-foam/extra_foam/config.py", line 393, in from_file
    raise OSError(msg)
OSError: Invalid config file: /home/username/.EXtra-foam/scs.config.yaml
ParserError('while parsing a block mapping', <yaml.error.Mark object at 0x7fcffbd84910>,
"expected <block end>, but found '<block mapping start>'", <yaml.error.Mark object at 0x7fcffbd84ed0>)

This error is triggered when the CONFIG FILE is not valid. Please correct it if you have modified the default one. Alternatively, you can delete it and let the program generate a default one for you.

No data is received¶

If EXtra-foam opens up fine and running it by clicking on start button does nothing, please make sure that relevant PipeToZeroMQ device is properly configured, activated and its data sent property is updating. This device can be configured only with the help of experts (data analysis support and beamline scientists).

Incorrect dependencies¶

If you happen to have some Python packages which are used in EXtra-foam but in the meanwhile installed in your ~/.local directory, anything bad can happen if they have different version numbers. In the best case, EXtra-foam crashes, for example, when it attempted to call a function which does not exist in your local installation, and you will immediately notice it. In the worst case, the software keeps running but the result is incorrect and the difference between the incorrect result and the correct one is unperceivable.

This is the downside of using Anaconda to deploy software. However, it is easy to track down the loathful Python package if you already have one or a few suspects. Assuming the module EXtra-foam/beta is loaded, you can check the suspect one-by-one by following the example below:

~ python
Python 3.7.3 (default, Mar 27 2019, 22:11:17)
[GCC 7.3.0] :: Anaconda, Inc. on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import redis
>>> print(redis.__file__)
# expected result :-)
/gpfs/exfel/sw/software/xfel_anaconda3/EXtra-foam-beta/lib/python3.7/site-packages/redis/__init__.py
# This is bad!
/home/username/.local/lib/python3.7/site-packages/redis/__init__.py

The remedy is simply. Run pip uninstall to remove your local installation.